Message 1 of a two-step random access procedure

ABSTRACT

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify that the UE is configured to use a two-step random access channel (RACH) procedure. The two-step RACH procedure may include an uplink request message and a downlink response. The UE may transmit the uplink request message as part of the two-step RACH procedure, and the uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes a physical uplink shared channel waveform. The UE may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

CROSS REFERENCE

The present application for patent claims the benefit of U.S.Provisional Patent Application No. 62/740,937 by ZHANG, et al., entitled“MESSAGE 1 OF A TWO-STEP RANDOM ACCESS PROCEDURE,” filed Oct. 3, 2018,assigned to the assignee hereof, and expressly incorporated herein.

BACKGROUND

The following relates generally to wireless communications, and morespecifically to methods and techniques for configuring and transmittinga first message, or message 1, of a two-step random access procedure.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-accesscommunications system may include a number of base stations or networkaccess nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

Some wireless systems may support random access procedures forestablishing communications between a UE and a base station. The randomaccess procedure may involve a series of handshake messages between theUE and the base station. In some cases, it may be desirable to reducethe latency associated with the random access procedure.

SUMMARY

The described techniques relate to improved methods, systems, devices,and apparatuses that support message 1 of a two-step random accessprocedure. Generally, the described techniques provide for performing atwo-step random access procedure based on an access request message(message 1) from a UE that includes a preamble portion and a payloadportion. In some instances, the preamble of the access request messagemay serve as a demodulation reference signal for a payload portion ofthe access request message. In some cases, the payload portion of theaccess request message may be a physical uplink control channel waveformor a physical uplink shared channel waveform. The size of the payloadportion of the access request message may be fixed or may be a functionof a random access procedure use case.

A method of wireless communication at a UE is described. The method mayinclude identifying that the UE is configured to use a two-step randomaccess channel (RACH) procedure, the two-step RACH procedure includingan uplink request message and a downlink response, transmitting theuplink request message as part of the two-step RACH procedure, theuplink request message including a preamble portion that is one of aplurality of predefined sequences and a payload portion that includes awaveform of a physical uplink shared channel, where the preamble portionis associated with a transmission occasion of the physical uplink sharedchannel, and receiving the downlink response as part of the two-stepRACH procedure and in response to the uplink request message.

An apparatus for wireless communication at a UE is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto identify that the UE is configured to use a two-step RACH procedure,the two-step RACH procedure including an uplink request message and adownlink response, transmit the uplink request message as part of thetwo-step RACH procedure, the uplink request message including a preambleportion that is one of a plurality of predefined sequences and a payloadportion that includes a waveform of a physical uplink shared channel,where the preamble portion is associated with a transmission occasion ofthe physical uplink shared channel, and receive the downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.

Another apparatus for wireless communication at a UE is described. Theapparatus may include means for identifying that the UE is configured touse a two-step RACH procedure, the two-step RACH procedure including anuplink request message and a downlink response, means for transmittingthe uplink request message as part of the two-step RACH procedure, theuplink request message including a preamble portion that is one of aplurality of predefined sequences and a payload portion that includes awaveform of a physical uplink shared channel, where the preamble portionis associated with a transmission occasion of the physical uplink sharedchannel, and means for receiving the downlink response as part of thetwo-step RACH procedure and in response to the uplink request message.

A non-transitory computer-readable medium storing code for wirelesscommunication at a UE is described. The code may include instructionsexecutable by a processor to identify that the UE is configured to use atwo-step RACH procedure, the two-step RACH procedure including an uplinkrequest message and a downlink response, transmit the uplink requestmessage as part of the two-step RACH procedure, the uplink requestmessage including a preamble portion that is one of a plurality ofpredefined sequences and a payload portion that that includes a waveformof a physical uplink shared channel, where the preamble portion isassociated with a transmission occasion of the physical uplink sharedchannel, and receive the downlink response as part of the two-step RACHprocedure and in response to the uplink request message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving an indicationof the preamble portion before transmitting the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message as a demodulation reference signal for thepayload portion of the uplink request message. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, transmitting the uplink request message may alsoinclude transmitting additional demodulation reference signals for thepayload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message using a preamble sequence that has a prime numbersequence length, and transmitting the payload portion using resourceelements that are a subset of a frequency span of the preamble portion.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the payload portion using apayload size that is based, at least in part, on whether the two-stepRACH procedure is for initial access or for handover. In some examplesof the method, apparatuses, and non-transitory computer-readable mediumdescribed herein, transmitting the uplink request message may includetransmitting the payload portion using a fixed payload size.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message back-to-back with the payload portion of theuplink request message, each resource element of the preamble portionand each resource element of the payload portion having a cyclic prefix.In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cyclic prefix of theresource elements of the preamble portion of the uplink request messageis different from the cyclic prefix of the resource elements of thepayload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message interleaved in time with the payload portion ofthe uplink request message, each resource element of the preambleportion and each resource element of the payload portion having a cyclicprefix. In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cyclic prefix of theresource elements of the preamble portion of the uplink request messageis different from the cyclic prefix of the resource elements of thepayload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message back-to-back with the payload portion of theuplink request message without use of cyclic prefixes between resourceelements of the preamble portion.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving, viaremaining minimum system information or radio resource controlsignaling, an association between the preamble portion of the uplinkrequest message and the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the preamble portion of theuplink request message during a first transmission time interval, andtransmitting, in accordance with the received association, the payloadportion of the uplink request message during a second transmission timeinterval. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, transmittingthe uplink request message may also include transmitting the preambleportion of the uplink request message and the payload portion of theuplink request message without an intervening transmission time intervalbetween the first transmission time interval and the second transmissiontime interval. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, transmittingthe uplink request message may also include transmitting the preambleportion of the uplink request message and the payload portion of theuplink request message with an intervening transmission time intervalbetween the first transmission time interval and the second transmissiontime interval, wherein the intervening transmission time interval isavailable for non-RACH transmissions.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for selecting a preamblesequence from the plurality of predefined sequences for transmission ofthe preamble portion of the uplink request message, wherein only aportion of the predefined sequences are associated with two-step RACHprocedures.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the payload portion of theuplink request message with an embedded demodulation reference signal tomatch dimensions of both the preamble portion and the payload portion.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include selecting a preamble sequence from theplurality of predefined sequences for transmission of the preambleportion of the uplink request message, wherein the selected preamblesequence shares a resource association with another preamble sequence ofthe plurality of predefined sequences, and applying an additionaldifferentiating factor to the uplink request message to allowdifferentiation of the payload portion of the uplink request message. Insome examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the additionaldifferentiating factor is one or more of use of different demodulationreference signal ports or use of different scrambling identifications.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for selecting a preamblesequence from the plurality of predefined sequences for transmission ofthe preamble portion of the uplink request message, wherein the selectedpreamble sequence has a resource association with more than one payloadresource, and applying an additional identifying factor to the uplinkrequest message to allow identification of the payload portion of theuplink request message. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the additionalidentifying factor is one or more of use of different demodulationreference signal ports or use of different scrambling identifications.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting the payload portion during atime resource that is time-multiplexed with payload portions fromadditional UEs. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, transmittingthe uplink request message may include transmitting the payload portionduring a time resource that is code division-multiplexed with payloadportions from additional UEs.

A method of wireless communication at a base station is described. Themethod may include receiving, as part of a two-step RACH procedure, anuplink request message from a UE, the uplink request message including apreamble portion that is one of a plurality of predefined sequences anda payload portion that includes a waveform of a physical uplink sharedchannel, where the preamble portion is associated with a transmissionoccasion of the physical uplink shared channel, and transmitting adownlink response as part of the two-step RACH procedure and in responseto the uplink request message.

An apparatus for wireless communication at a base station is described.The apparatus may include a processor, memory in electroniccommunication with the processor, and instructions stored in the memory.The instructions may be executable by the processor to cause theapparatus to receive, as part of a two-step RACH procedure, an uplinkrequest message from a UE, the uplink request message including apreamble portion that is one of a plurality of predefined sequences anda payload portion includes a waveform of a physical uplink sharedchannel, where the preamble portion is associated with a transmissionoccasion of the physical uplink shared channel, and transmit a downlinkresponse as part of the two-step RACH procedure and in response to theuplink request message.

Another apparatus for wireless communication at a base station isdescribed. The apparatus may include means for receiving, as part of atwo-step RACH procedure, an uplink request message from a UE, the uplinkrequest message including a preamble portion that is one of a pluralityof predefined sequences and a payload portion that includes a waveformof a physical uplink shared channel, where the preamble portion isassociated with a transmission occasion of the physical uplink sharedchannel, and means for transmitting a downlink response as part of thetwo-step RACH procedure and in response to the uplink request message.

A non-transitory computer-readable medium storing code for wirelesscommunication at a base station is described. The code may includeinstructions executable by a processor to receive, as part of a two-stepRACH procedure, an uplink request message from a UE, the uplink requestmessage including a preamble portion that is one of a plurality ofpredefined sequences and a payload portion that includes a waveform of aphysical uplink shared channel, where the preamble portion is associatedwith a transmission occasion of the physical uplink shared channel, andtransmit a downlink response as part of the two-step RACH procedure andin response to the uplink request message.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting anindication of the preamble portion to the UE before receiving the uplinkrequest message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, receiving the uplink requestmessage may include receiving the preamble portion of the uplink requestmessage, and using the preamble portion of the uplink request message asa demodulation reference signal for the payload portion of the uplinkrequest message. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, transmittingthe uplink request message may also include receiving additionaldemodulation reference signals for the payload portion of the uplinkrequest message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message using a preamble sequence that has a prime numbersequence length, and receiving the payload portion using resourceelements that are a subset of a frequency span of the preamble portion.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the payload portion using apayload size that is based, at least in part, on whether the two-stepRACH procedure is for initial access or for handover. In some examplesof the method, apparatuses, and non-transitory computer-readable mediumdescribed herein, transmitting the uplink request message may includereceiving the payload portion using a fixed payload size.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message back-to-back with the payload portion of the uplinkrequest message, each resource element of the preamble portion and eachresource element of the payload portion having a cyclic prefix. In someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cyclic prefix of theresource elements of the preamble portion of the uplink request messageis different from the cyclic prefix of the resource elements of thepayload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message interleaved in time with the payload portion of theuplink request message, each resource element of the preamble portionand each resource element of the payload portion having a cyclic prefix.In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the cyclic prefix of theresource elements of the preamble portion of the uplink request messageis different from the cyclic prefix of the resource elements of thepayload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message back-to-back with the payload portion of the uplinkrequest message without use of cyclic prefixes between resource elementsof the preamble portion.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include transmitting, via remaining minimum systeminformation or radio resource control signaling, an association betweenthe preamble portion of the uplink request message and the payloadportion of the uplink request message. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, transmitting the uplink request message may include receivingthe preamble portion of the uplink request message during a firsttransmission time interval, and receiving, in accordance with thetransmitted association, the payload portion of the uplink requestmessage during a second transmission time interval.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message and the payload portion of the uplink request messagewithout an intervening transmission time interval between the firsttransmission time interval and the second transmission time interval. Insome examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the preamble portion of the uplinkrequest message and the payload portion of the uplink request messagewith an intervening transmission time interval between the firsttransmission time interval and the second transmission time interval,wherein the intervening transmission time interval is available fornon-RACH transmissions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving in the preamble portion a preamblesequence selected from the plurality of predefined sequences, whereinonly a portion of the predefined sequences are associated with two-stepRACH procedures. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, transmittingthe uplink request message may include receiving the payload portion ofthe uplink request message with an embedded demodulation referencesignal to match dimensions of both the preamble portion and the payloadportion.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving in the preamble portion a preamblesequence selected from the plurality of predefined sequences, whereinthe selected preamble sequence shares a resource association withanother preamble sequence of the plurality of predefined sequences, anddifferentiating the payload portion of the uplink request message via adifferentiating factor. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, thedifferentiating factor is one or more of use of different demodulationreference signal ports or use of different scrambling identifications.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving in the preamble portion a preamblesequence selected from the plurality of predefined sequences, whereinthe selected preamble sequence has a resource association with more thanone payload resource, and identifying the payload portion of the uplinkrequest message via an identifying factor. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the identifying factor is one or more of use ofdifferent demodulation reference signal ports or use of differentscrambling identifications.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the payload portion during a timeresource that is time-multiplexed with payload portions from additionalUEs. In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include receiving the payload portion during a timeresource that is code division-multiplexed with payload portions fromadditional UEs.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the uplinkrequest message may include applying the preamble portion of the uplinkrequest message as a demodulation reference signal for the payloadportion of the uplink request message, and scheduling non-RACHtransmissions based on presence of the preamble portion and applicationof the preamble portion as a demodulation reference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationsthat supports message 1 of a two-step random access procedure inaccordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a process that supports message 1 of atwo-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 3 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 4 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 5 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 6 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 7 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 8 illustrates an example of a message configuration for message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure.

FIGS. 9 and 10 show block diagrams of devices that support message 1 ofa two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 11 shows a block diagram of a communications manager that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure.

FIG. 12 shows a diagram of a system including a device that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure.

FIGS. 13 and 14 show block diagrams of devices that support message 1 ofa two-step random access procedure in accordance with aspects of thepresent disclosure.

FIG. 15 shows a block diagram of a communications manager that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure.

FIG. 16 shows a diagram of a system including a device that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure.

FIGS. 17 and 18 show flowcharts illustrating methods that supportmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

Some wireless systems support establishment of communications between auser equipment (UE) and a base station using a random access procedurethat may enable a UE to synchronize with the base station. The UE mayinitiate the random access procedure when it is first powered up (e.g.,at initial access), during a handover of the UE from one base station toanother base station, when the UE needs to re-establish communicationsafter an interruption, or under various other conditions, for example.

In some cases, a random access procedure may include transmission of aseries of four handshake messages between the UE and the base station.Such messages may be unscheduled, for example, and may be transmitted ona shared random access channel (RACH). When the random access procedureis used in an unlicensed spectrum, the UE may perform alisten-before-talk (LBT) procedure before transmitting each message toensure that the transmission channel is clear for use.

In a four-message random access procedure, the first message may be amessage transmitted from the UE to the base station and may include apreamble waveform (e.g., a preamble sequence) that identifies the UE.The second message may be transmitted from the base station to the UEand may acknowledge receipt of the preamble and allocate transmissionresources to the UE. The third message may be another messagetransmitted from the UE to the base station and may include a requestfor a radio resource control (RRC) connection. The fourth message may betransmitted from the base station to the UE and may include an RRCconnection response. Once the fourth message is received and decoded bythe UE, the UE may begin communications with the base station in, forexample, RRC connected mode. This random access procedure may bereferred to as a four-step random access procedure.

In some cases, it may be desirable or beneficial to reduce the latencyand/or the number of LBT procedures associated with performing a randomaccess procedure. Such reductions may improve communication efficiencyand may be particularly useful for latency-sensitive communications.Thus, new random access procedures may be needed to reduce the latencyassociated with the random access procedure.

Aspects of the present disclosure may include a two-step random accessprocedure that includes transmission of a first message (message 1) fromthe UE to the base station and a second message (message 2) from thebase station to the UE. In some cases, these two messages mayessentially replace the four messages of a conventional four-step randomaccess procedure. As described herein, in some cases, a UE may beconfigured to support both the two-step random access procedure and thefour-step random access procedure.

In some cases, message 1 of the two-step random access procedureincludes a preamble portion and a payload portion (which may be, forexample, an RRC connection request or data), thereby combining featuresof the first message and the third message of a conventional four-stepprocedure. In some cases, the base station may respond with a downlinkresponse. This downlink response may be referred to as message 2 of thetwo-step random access procedure.

As described herein, a two-step random access procedure may providemultiple benefits. For example, a two-step random access procedure asdescribed herein may reduce the number of messages required for a randomaccess procedure and may correspondingly, reduce the number of LBTprocedures that may be performed by the UE when the UE is operating inan unlicensed spectrum. Such reductions may reduce the latency of therandom access procedure. In addition, in some cases, the preambleportion of message 1 may be used as a reference signal for the payloadportion of message 1, which may be particularly beneficial in thecontext of high Doppler operation (such as in vehicle to everything(V2X) systems) when a UE may be moving relatively quickly.

Aspects of the disclosure are initially described in the context of awireless communications system. Aspects of the disclosure are furtherdescribed in the context of a process flow. Aspects of the disclosureare further illustrated by and described with reference to messageconfiguration diagrams, apparatus diagrams, system diagrams, andflowcharts that relate to configuring and transmitting message 1 of atwo-step random access procedure.

FIG. 1 illustrates an example of a wireless communications system 100that supports message 1 of a two-step random access procedure inaccordance with aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or a New Radio (NR) network. In somecases, wireless communications system 100 may support enhanced broadbandcommunications, ultra-reliable (e.g., mission critical) communications,low latency communications, or communications with low-cost andlow-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation Node B orgiga-nodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up only a portion of the geographic coverage area110, and each sector may be associated with a cell. For example, eachbase station 105 may provide communication coverage for a macro cell, asmall cell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples half-duplexcommunications may be performed at a reduced peak rate. Other powerconservation techniques for UEs 115 include entering a power saving“deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1, N2, N3, orother interface). Base stations 105 may communicate with one anotherover backhaul links 134 (e.g., via an X2, Xn, or other interface) eitherdirectly (e.g., directly between base stations 105) or indirectly (e.g.,via core network 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 MHz to 300 GHz.Generally, the region from 300 MHz to 3 GHz is known as the ultra-highfrequency (UHF) region or decimeter band, since the wavelengths rangefrom approximately one decimeter to one meter in length. UHF waves maybe blocked or redirected by buildings and environmental features.However, the waves may penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Transmission of UHFwaves may be associated with smaller antennas and shorter range (e.g.,less than 100 km) compared to transmission using the smaller frequenciesand longer waves of the high frequency (HF) or very high frequency (VHF)portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that can tolerate interference from otherusers.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band (NR-U) such as the 5 GHz ISM band. When operatingin unlicensed radio frequency spectrum bands, wireless devices such asbase stations 105 and UEs 115 may employ LBT procedures to ensure afrequency channel is clear before transmitting data. In some cases,operations in unlicensed bands may be based on a CA configuration inconjunction with CCs operating in a licensed band (e.g., LAA).Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, peer-to-peer transmissions, or a combination ofthese. Duplexing in unlicensed spectrum may be based on frequencydivision duplexing (FDD), time division duplexing (TDD), or acombination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving devices are equipped with one ormore antennas. MIMO communications may employ multipath signalpropagation to increase the spectral efficiency by transmitting orreceiving multiple signals via different spatial layers, which may bereferred to as spatial multiplexing. The multiple signals may, forexample, be transmitted by the transmitting device via differentantennas or different combinations of antennas. Likewise, the multiplesignals may be received by the receiving device via different antennasor different combinations of antennas. Each of the multiple signals maybe referred to as a separate spatial stream, and may carry bitsassociated with the same data stream (e.g., the same codeword) ordifferent data streams. Different spatial layers may be associated withdifferent antenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO) where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO) where multiple spatial layers are transmitted to multipledevices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105. Some signals, such as datasignals associated with a particular receiving device, may betransmitted by a base station 105 in a single beam direction (e.g., adirection associated with the receiving device, such as a UE 115). Insome examples, the beam direction associated with transmissions along asingle beam direction may be determined based at least in in part on asignal that was transmitted in different beam directions. For example, aUE 115 may receive one or more of the signals transmitted by the basestation 105 in different directions, and the UE 115 may report to thebase station 105 an indication of the signal it received with a highestsignal quality, or an otherwise acceptable signal quality. Althoughthese techniques are described with reference to signals transmitted inone or more directions by a base station 105, a UE 115 may employsimilar techniques for transmitting signals multiple times in differentdirections (e.g., for identifying a beam direction for subsequenttransmission or reception by the UE 115), or transmitting a signal in asingle direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a plurality of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a plurality of antenna elements of anantenna array, any of which may be referred to as “listening” accordingto different receive beams or receive directions. In some examples areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based at least inpart on listening according to different receive beam directions (e.g.,a beam direction determined to have a highest signal strength, highestsignal-to-noise ratio, or otherwise acceptable signal quality based atleast in part on listening according to multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A Medium Access Control (MAC) layer may performpriority handling and multiplexing of logical channels into transportchannels. The MAC layer may also use hybrid automatic repeat request(HARQ) to provide retransmission at the MAC layer to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer may provide establishment, configuration, and maintenanceof an RRC connection between a UE 115 and a base station 105 or corenetwork 130 supporting radio bearers for user plane data. At thePhysical (PHY) layer, transport channels may be mapped to physicalchannels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ may include acombination of error detection (e.g., using a cyclic redundancy check(CRC)), forward error correction (FEC), and retransmission (e.g.,automatic repeat request (ARQ)). HARQ may improve throughput at the MAClayer in poor radio conditions (e.g., signal-to-noise conditions). Insome cases, a wireless device may support same-slot HARQ feedback, wherethe device may provide HARQ feedback in a specific slot for datareceived in a previous symbol in the slot. In other cases, the devicemay provide HARQ feedback in a subsequent slot, or according to someother time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period ofT_(s)=1/30,720,000 seconds. Time intervals of a communications resourcemay be organized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an E-UTRA absolute radiofrequency channel number (EARFCN)), and may be positioned according to achannel raster for discovery by UEs 115. Carriers may be downlink oruplink (e.g., in an FDD mode), or be configured to carry downlink anduplink communications (e.g., in a TDD mode). In some examples, signalwaveforms transmitted over a carrier may be made up of multiplesub-carriers (e.g., using multi-carrier modulation (MCM) techniques suchas OFDM or DFT-s-OFDM).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR,etc.). For example, communications over a carrier may be organizedaccording to TTIs or slots, each of which may include user data as wellas control information or signaling to support decoding the user data. Acarrier may also include dedicated acquisition signaling (e.g.,synchronization signals or system information, etc.) and controlsignaling that coordinates operation for the carrier. In some examples(e.g., in a carrier aggregation configuration), a carrier may also haveacquisition signaling or control signaling that coordinates operationsfor other carriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations105 or UEs 115) may have a hardware configuration that supportscommunications over a particular carrier bandwidth, or may beconfigurable to support communications over one of a set of carrierbandwidths. In some examples, the wireless communications system 100 mayinclude base stations 105 and/or UEs 115 that can support simultaneouscommunications via carriers associated with more than one differentcarrier bandwidth.

Wireless communications system 100 may support communication with a UE115 on multiple cells or carriers, a feature which may be referred to ascarrier aggregation (CA) or multi-carrier operation. A UE 115 may beconfigured with multiple downlink CCs and one or more uplink CCsaccording to a carrier aggregation configuration. Carrier aggregationmay be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation configuration or a dual connectivity configuration (e.g.,when multiple serving cells have a suboptimal or non-ideal backhaullink). An eCC may also be configured for use in unlicensed spectrum orshared spectrum (e.g., where more than one operator is allowed to usethe spectrum). An eCC characterized by wide carrier bandwidth mayinclude one or more segments that may be utilized by UEs 115 that arenot capable of monitoring the whole carrier bandwidth or are otherwiseconfigured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased spacing between adjacent subcarriers. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., according to frequency channel orcarrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symboldurations (e.g., 16.67 microseconds). A TTI in eCC may consist of one ormultiple symbol periods. In some cases, the TTI duration (that is, thenumber of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize anycombination of licensed, shared, and unlicensed spectrum bands, amongothers. The flexibility of eCC symbol duration and subcarrier spacingmay allow for the use of eCC across multiple spectrums. In someexamples, NR shared spectrum may increase spectrum utilization andspectral efficiency, specifically through dynamic vertical (e.g., acrossthe frequency domain) and horizontal (e.g., across the time domain)sharing of resources.

In some cases, a UE 115 may perform a random access procedure tosynchronize with the network under various circumstances, including atpower-up (e.g., for initial access) or at a handover from one basestation 105 to another base station 105, for example. The random accessprocedure may enable the UE 115 to synchronize timing with the basestation 105 and receive an allocation of uplink transmission resources.In some cases, a UE 115 may perform a two-step random access procedure.The UE 115 may initiate the procedure by transmitting an uplink requestmessage (message 1) to a base station 105. The uplink request messagemay include a preamble portion and a payload portion.

In some cases, the UE 115 may transmit the uplink request message to thebase station using a transport channel, such as a shared RACH. Thus, thetwo-step random access procedure may be referred to as a two-step RACHprocedure.

In some cases, the preamble portion of message 1 is a sequence, such asa Zadoff-Chu sequence or another type of sequence. In some cases, thesequence may have the property that cyclically shifted versions of thesequence are orthogonal to one another, such that the sequence may beused to reduce cross-correlation (e.g., interference) betweentransmissions.

In some cases, the preamble sequence (e.g., the sequence selected forthe preamble portion) may be randomly selected from a set of predefinedsequences. This may enable the base station 105 to distinguish betweenmultiple UEs 115 trying to access the system simultaneously, since RACHis normally contention-based.

In some cases, the preamble portion (e.g., the preamble sequence) may beassociated with a transmission occasion of a physical uplink sharedchannel (PUSCH). For example, the preamble portion may indicate anoccasion during which the UE may transmit information to the basestation on the PUSCH.

In some cases, the UE may receive an indication of the preamble portionfrom the base station before transmitting the uplink request message.For example, the base station may select a preamble sequence and maytransmit an indication of the preamble sequence to the UE, and theindicated preamble sequence may be included by the UE in the preambleportion of the uplink request message.

In some cases, the payload portion includes either a physical uplinkcontrol channel (PUCCH) waveform or a PUSCH waveform. A PUCCH waveformmay be used to convey signaling or control information, for example. APUSCH waveform may be used to convey signaling information, uplinkcontrol information (UCI), or user data, for example.

In some cases, the base station 105 may respond to receiving message 1from the UE 115 by transmitting a downlink response that enables the UE115 to begin ongoing communication with the base station 105 (e.g., byestablishing an RRC connection), thereby completing the two-step RACHprocedure.

In some cases, a UE 115 may identify that the UE 115 is configured touse a two-step RACH procedure. The two-step RACH procedure may includean uplink request message and a downlink response. The UE 115 maytransmit the uplink request message as part of the two-step RACHprocedure. The uplink request message may include a preamble portionthat is one of a set of predefined sequences and a payload portion thatincludes either a PUCCH waveform or a PUSCH waveform, where the preambleportion is associated with a transmission occasion of the PUSCH. The UE115 may receive the downlink response as part of the two-step RACHprocedure and in response to the uplink request message.

In some cases, a base station 105 may receive, as part of a two-stepRACH procedure, an uplink request message from a UE. The uplink requestmessage may include a preamble portion that is one of a set ofpredefined sequences and a payload portion that includes either a PUCCHwaveform or a PUSCH waveform, where the preamble portion is associatedwith a transmission occasion of the PUSCH. The base station 105 maytransmit a downlink response as part of the two-step RACH procedure andin response to the uplink request message.

UEs 115 may include a UE communications manager 102, which may identifythat the UE 115 is configured to use a two-step RACH procedure. Thetwo-step RACH procedure may include an uplink request message and adownlink response. The UE communications manager 102 may transmit theuplink request message as part of the two-step RACH procedure, theuplink request message including a preamble portion that is one of a setof predefined sequences and a payload portion that includes either aphysical uplink control channel waveform or a physical uplink sharedchannel waveform, where the preamble portion is associated with atransmission occasion of the PUSCH. The UE communications manager 102may receive the downlink response as part of the two-step RACH procedureand in response to the uplink request message.

One or more of the base stations 105 may include a base stationcommunications manager 101, which may receive, as part of a two-stepRACH procedure, an uplink request message from a UE 115. The uplinkrequest message including a preamble portion that is one of a set ofpredefined sequences and a payload portion that includes either aphysical uplink control channel waveform or a physical uplink sharedchannel waveform, where the preamble portion is associated with atransmission occasion of the PUSCH. The base station communicationsmanager 101 may transmit a downlink response as part of the two-stepRACH procedure and in response to the uplink request message.

FIG. 2 illustrates an example of a process 200 that supports a two-steprandom access procedure (e.g., a two-step RACH procedure) in accordancewith aspects of the present disclosure. In some examples, process 200may implement aspects of wireless communication system 100. Process 200may include communications between a base station 205 and a UE 210,which may be examples of the corresponding devices described herein.

At 215, UE 210 may identify that the UE 210 is configured to use atwo-step RACH procedure. The UE 210 may identify that the UE 210 isconfigured to use the two-step RACH procedure based on configurationinformation previously received by UE 210 or based on a device settingof UE 210, for example.

At 220, UE 210 may transmit an uplink request message as part of thetwo-step RACH procedure. In some cases, the UE 210 may transmit theuplink request message on the RACH transport channel, for example. Insome cases, the uplink request message may include a preamble portionthat is one of a set of predefined sequences and a payload portion thatincludes either a PUCCH waveform or a PUSCH waveform. In some cases, thepreamble portion is associated with a transmission occasion of thePUSCH.

At 225, base station 205 may, in response to receiving the uplinkrequest message from UE 210, transmit a downlink response to UE 210 thatmay be received by UE 210.

At 230, UE 210 may, based on the downlink response message received frombase station 205, begin communicating with base station 205. In somecases, UE 210 may begin communicating in RRC connected mode, forexample.

Additional details regarding aspects of the uplink request message aredescribed in more detail with reference to FIGS. 3 through 8.

FIG. 3 illustrates an example of a message configuration 300 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 300 may betransmitted using aspects of wireless communication system 100.

Message configuration 300 includes uplink request message 305 that maybe transmitted from a UE 210 to a base station 205 as described withrespect to FIG. 2. Uplink request message 305 may include a preambleportion 310 and a payload portion 325.

Preamble portion 310 may include one or more preamble resource elements315-a through 315-b, each of which may include a symbol, such as an OFDMsymbol, and a preamble cyclic prefix 320. Preamble cyclic prefixes 320may serve as guard intervals to reduce inter-symbol interference betweenpreamble resource elements 315, and/or may be used to support channelestimation or equalization. The preamble portion 310 may be associatedwith a PUCCH or PUSCH occasion (e.g., a transmission occasion duringwhich the UE may transmit information on the PUCCH or PUSCH), forexample. Preamble resource elements 315 may be indexed as shown from 0to 11, for example, if there are twelve preamble resource elements in afrequency band. Other numbers of preamble resource elements arepossible.

In some cases, preamble portion 310 is or includes one of a set ofpredefined sequences, such as Zadoff-Chu sequences or other type ofsequences, for example. In some cases, the set of predefined sequencesmay be a set of 64 Zadoff-Chu sequences, for example. In some cases, thepredefined sequence may be known to both the UE 210 and the base station205. In some cases, preamble portion 310 includes a sequence having asequence length that is a prime number. In some cases, each of thesequences in the set of predefined sequences have corresponding sequencelengths that are prime numbers. The UE 210 may select the predefinedsequence randomly, for example, or using a selection algorithm.

In some cases, base station 205 may transmit an indication of thepreamble portion (e.g., a preamble sequence) to UE 210, and UE 210 mayselect the predefined sequence based on the indication received from thebase station 205.

Payload portion 325 includes one or more payload resource elements 330-athrough 33-b, each of which may include a symbol, such as an OFDM orDFT-s-OFDM symbol, and a payload cyclic prefix 335. Payload cyclicprefixes 335 may serve as guard intervals to reduce inter-symbolinterference between payload resource elements 330, and/or may be usedto support channel estimation or equalization.

In some cases, the payload cyclic prefix 335 may be the same as thepreamble cyclic prefix 320. For example, the payload cyclic prefix 335may have the same length as the preamble cyclic prefix 320. In somecases, the payload cyclic prefix 335 may be different than the preamblecyclic prefix 320. For example, the payload cyclic prefix 335 may have adifferent length than the preamble cyclic prefix 320.

As depicted in FIG. 3, in some cases, the preamble portion 310 and thepayload portion 325 are transmitted back-to-back; that is, there may notbe a gap between the last preamble resource element and the firstpayload resource element. In this case, the payload portion 325 may beappended to the preamble portion 310. In some cases, the preambleportion 310 and the payload portion 325 may be transmitted back-to-backon the same resources.

In some cases, the payload portion 325 may be transmitted as a PUCCHwaveform or a PUSCH waveform. In some cases, payload portion 325includes signaling or control information, such as an RRC request (e.g.,a request for an RRC connection) for an initial access. The signaling orcontrol information may be transmitted as a PUCCH waveform, for example.In some cases, payload portion 325 includes user data. Such user datamay include, for example, data transmitted within a V2X system, such asa user (vehicle) location or speed. In some cases, the user data may betransmitted as a PUCCH or PUSCH waveform, for example. In some cases,the user data may be transmitted in a two-step RACH procedure during ahandover, for example.

In some cases, the payload portion 325 may have a fixed payload size(which may include padding). That is, the payload portion 325 may betransmitted using the same fixed payload size regardless of whether thetwo-step RACH procedure is initiated for an initial access (e.g., onpower up), for a handover, or for another reason.

In some cases, the payload portion 325 may have a payload size that isbased on whether the two-step RACH procedure is initiated for an initialaccess or for a handover. For example, the payload portion 325 may betransmitted using a smaller payload size for an initial access (in whichthe payload may include an RRC connection request) and using a largerpayload size for a handover (in which the payload may include userdata), or vice versa.

As depicted in FIG. 3, in some cases, uplink request message 305 may betransmitted using interlaces 350. An interlace 350 may be a set offrequency resources used for transmissions over a channel (e.g., PUCCH,PUSCH) to mitigate issues related to power spectral density limitations,for example. An interlace may include M resource block clusters 345 thatare evenly spaced across the frequency span 340 (e.g., the systembandwidth available for the transmission), which may be, in thisexample, 20 MHz. Each resource block cluster 345 may include Ninterlaces 350. In some cases, an interlace 350 may be associated withtransmission of a preamble portion 310.

In other cases, an uplink request message 305 may be transmitted withoutusing interlaces; e.g., using a contiguous preamble format.

In some cases, the preamble portion 305 and payload portion 325 may havealigned resource element boundaries, as depicted in FIG. 3. In thiscase, an interlaced preamble (e.g., having a cyclic prefix for eachsequence transmission) may be reused as a reference signal, such as ademodulation reference signal (DMRS) or other reference signal, for thepayload portion 325. Thus, in some cases, the preamble portion 310 ofthe uplink request message 305 may be transmitted as a DMRS for thepayload portion 325 of the uplink request message 305.

In conventional systems, a DMRS for a payload may be have a length thatis a multiple of the number of resource elements associated with thepayload. Therefore, the length of a DMRS is, in general, not a primenumber. However, when the preamble portion 310, which has a sequencelength that is a prime number, is used as a DMRS for the payload portion325, the payload portion 325 may be transmitted using a number ofresource elements that is the same prime number as the sequence lengthto enable the DMRS to be used as a reference signal for the payloadportion 325. In this case, this number of resource elements used totransmit the payload portion 325 may be a subset of the frequency spanof the preamble portion 310; that is, some resource elements 330-b maynot be used. This scenario may be particularly relevant to the case oftransmissions using DFT-s-OFDM symbols, for example.

In some cases, a preamble cyclic prefix 320 of a preamble resourceelement 315 in the preamble portion 310 may include a cyclic prefixextension; e.g., the preamble cyclic prefix 320 may be extended to alarger length or longer time period to enable the preamble portion 310to be used as a DMRS for payload portion 330.

In some cases, the uplink request message 305 may include one or moreadditional reference signals (e.g., one or more additional DMRS's orother reference signals) for the payload portion 325, either in additionto or instead of the DMRS transmitted in the preamble portion 310.

In some cases, the preamble portion 310 and payload portion 325 may havedifferent user multiplexing capabilities. For example, the preambleportion 310 may be a PUCCH waveform, which may be designed to carry(e.g., accommodate transmissions from) multiple UEs using, for example,FDM and/or code division multiplexing (CDM). For example, the payloadportion 325 may be a PUSCH waveform, which may not be designed to carrymultiple UEs. In some cases, it may be possible to spatially separatetransmissions from multiple UEs on a PUSCH waveform.

In some cases, the payload portion 325 may be frequency divisionmultiplexed or code division multiplexed across UEs 210.

In some cases, the uplink request message 305 may not include (e.g., mayomit) HARQ information if the random access procedure is acontention-based random access procedure (CBRA); e.g., for use in NR-Uor another unlicensed spectrum.

FIG. 4 illustrates an example of a message configuration 400 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 400 may betransmitted using aspects of wireless communication system 100.

Message configuration 400 includes uplink request message 405, which maybe transmitted by a UE 210 to a base station 205 as described withrespect to FIG. 2. Uplink request message 405 may include a preambleportion 410 and a payload portion 425. In some cases, the uplink requestmessage 405 may be transmitted using interlaces. In some cases, theuplink request message 405 may be transmitted without using interlaces.

In message configuration 400, preamble resource elements 415 of preambleportion 410 are interleaved in time (e.g., multiplexed in time) withpayload resource elements 440 of payload portion 425. In this example,the interleaved preamble resource elements 415 and payload resourceelements 440 have resource element boundaries that are aligned in time,and the preamble portion 410 is distributed in time for better detection(e.g., better synchronization) under high Doppler conditions, such as ina V2X system in which UEs 210 may be moving relatively quickly. Forexample, a first preamble resource element 415-a (e.g., a first preambleresource element spanning a frequency range at a given symbol) may beused as a DMRS for a corresponding first payload resource element 440-a(e.g., for a payload resource element that is adjacent in time to thefirst preamble resource element), and a second preamble resource element415-c may be used as a DMRS for a second payload resource element 440-c,etc. In some cases, preamble resource elements 415 may be transmittedback-to-back with payload resource elements 440 (e.g., without a gapbetween resource elements).

FIG. 5 illustrates an example of a message configuration 500 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 500 may betransmitted using aspects of wireless communication system 100.

Message configuration 500 includes uplink request message 505, which maybe transmitted by a UE 210 to a base station 205 as described withrespect to FIG. 2. Uplink request message 505 may include a preambleportion 510 and a payload portion 525. In some cases, the uplink requestmessage 505 may be transmitted using interlaces. In some cases, theuplink request message 505 may be transmitted without using interlaces.Preamble portion 510 may include preamble resource elements 515-athrough 515-b. Payload portion 525 may include payload resource elements530-a through 530-b.

In the example of message configuration 500, the preamble portion 510and the payload portion 525 are transmitted back-to-back; that is, theremay not be a gap between the last preamble resource element 515-b andthe first payload resource element 530-a. In this case, the payloadportion 525 may be appended to the preamble portion 510. In some cases,the preamble portion 510 and the payload portion 525 may be transmittedback-to-back on the same resources.

In some cases, the first preamble resource element 515-a in the preambleportion 510 may include a cyclic prefix 520, and subsequent preambleresource elements 515 may be transmitted without the use of cyclicprefixes between the preamble resource elements 515. That is, in somecases, only the first preamble resource element 515-a of a preambleportion 510 may include a cyclic prefix 520.

In some cases, the last preamble resource element 515-b in the preambleportion 510 may include a guard time (GT) 540. A guard time 540 may be ashort time interval that provides a buffer between the last preambleresource element 515-b and the first payload resource element 530-a toreduce the likelihood of inter-symbol interference.

FIG. 6 illustrates an example of a message configuration 600 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 600 may betransmitted using aspects of wireless communication system 100. Messageconfiguration 600 may depict an example of a message configuration thatmay provide backward-compatibility with the four-message random accessprocedure, as described herein.

Message configuration 600 includes uplink request message 605, which maybe transmitted by a UE 210 to a base station 205 as described withrespect to FIG. 2. Uplink request message 605 may include a preambleportion 610 and a payload portion 625. In some cases, the uplink requestmessage 605 may be transmitted using interlaces. In some cases, theuplink request message 605 may be transmitted without using interlaces.

In some cases, the first preamble resource element 615-a in the preambleportion 610 may include a preamble cyclic prefix 620, and the subsequentpreamble resource elements may be transmitted without the use ofpreamble cyclic prefixes 620 between the preamble resource elements 615.That is, in some cases, only the first preamble resource element 615-aof a preamble portion 610 may include a preamble cyclic prefix 620. Insome cases, the last preamble resource element 615-b in the preambleportion 610 may include a guard time (GT) 640.

In some cases, it may be desirable for a communication system to supportboth two-step random access procedures and four-step random accessprocedures, by, for example, using the same physical RACH (PRACH)configuration for both types of procedures. In some cases, such as inNR, the PRACH configuration index may determine the RACH occasion (RO)(e.g., a transmission occasion during which a UE may transmitinformation) in the time domain. In some cases, the general PRACHconfiguration may be kept the same for the two-step procedure andfour-step procedure, with the addition of an indication of theassociation between the preamble portion (e.g., the sequence) and thePUCCH/PUSCH resources allocated for transmission of the payload portionwhen the two-step random access procedure is used. That is, in somecases, a base station 205 may indicate, to the UE 210, an associationbetween a preamble and a payload resource (e.g., a PUCCH or PUSCHresource) for each RACH occasion.

The base station 205 may signal the association between the preamble andthe PUCCH/PUSCH resources in remaining minimum system information (RMSI)transmitted by the base station 205 to the UE 210. In this case, thePUCCH/PUSCH may be transmitted on a separate TTI (e.g., slot, mini-slot,resource element) than the preamble. That is, in some cases, messageconfiguration 600 may provide better compatibility with a four-step RACHprocedure by transmitting the preamble portion 610 of uplink requestmessage 605 during a first TTI (e.g., a slot) and transmitting thepayload portion 625 during a second TTI.

In some cases, the preamble portion 610 and the payload portion 625 maybe transmitted with an intervening TTI; e.g., there may be a third TTIthat is between the first TTI and the second TTI. In some cases, theintervening TTI may be available for non-RACH transmissions.

In some cases, the UE 210 may perform a first LBT procedure beforetransmitting the preamble portion 610 in the first TTI, and, becausethere is an intervening TTI during which the resources may be used byanother UE, UE 210 may perform a second LBT procedure beforetransmitting the payload portion 625 in the second TTI. In some cases,the additional LBT procedure may introduce undesirable latency in theRACH procedure.

In some cases, however, a base station 205 may use the intervening TTIto perform a downlink transmission, thereby occupying the resourcesduring the intervening TTI. In this case, the UE 210 may refrain fromperforming another LBT procedure before transmitting the payload portion625 of the uplink request message 605, thereby potentially reducing thelatency of the RACH procedure and enabling a more efficient use ofresources.

In some cases, a base station 205 may overprovision resources for thepayload portion 625 to ensure that sufficient resources are available toaccommodate potentially large payload sizes. However, in some cases,resources that have been provisioned by base station 205 for a preamblenay not be used; for example, a UE 210 may not use an allocated preambleresource to initiate a RACH procedure. In this case, the correspondingpayload resource may also be unused.

In some cases, if there is a gap (e.g., an intervening TTI) between thepreamble portion 610 and the payload portion 625, a base station 205 mayuse DMRS detection in the preamble portion 610 to schedule (e.g.,re-allocate) some of the corresponding payload portion 625 resources forwhich no preamble has been received (e.g., in the case when a UE doesnot initiate a RACH procedure on the preamble resource). In some cases,the base station 205 need only determine whether a UE 215 hastransmitted or not. In some cases, a base station 205 may have a fairlyshort amount of time in which to reschedule the resources. If the basestation 205 can process in a limited fashion due to smaller processingtime, the base station 205 can schedule some other UEs only on theresources it can process.

The payload resources may or may not fully overlap with the preambleresources. For example, preambles on one interlace may correspond to thepayload dimension across more than one interlace. In some cases, if apreamble portion overlaps a payload portion in frequency, then thepreamble portion may be used as a DMRS for the payload portion. In somecases, as shown in FIG. 6, the preamble portion 610 may not overlap thepayload portion 625 in frequency. In this case, the payload portion 625may include an embedded DMRS that matches the dimension (e.g., the sizeor number of resource elements 615, 630) of the preamble portion 610and/or the payload portion 625.

In some cases, a first portion of the set of predefined sequences may beassociated with two-step RACH procedures, and a second portion of theset of predefined sequences may be associated with four-step RACHprocedures. For example, if the set of sequences includes 64 sequences,the first portion may include 16 of the sequences that are associatedwith the two-step procedure, and the second portion may include 48 ofthe sequences that are associated with the four-step procedure. Otherpartitionings are possible.

In this case, a UE 210 may be configured (e.g., using RMSI) to select apreamble sequence (e.g., a sequence to be included in the preambleportion) from the first portion of the set of predefined sequences toperform a two-step RACH procedure, and the UE 210 may be configured toselect a preamble sequence from the second portion of the set ofpredefined sequences to perform a four-step RACH procedure. In thismanner, the preamble sequence may be used to indicate which randomaccess procedure (two-step or four-step) will be used.

In some cases, sequences that are included in the first portion ofsequences may be associated with two-step PUSCH/PUCCH resources, andsequences that are included in the second portion of sequences may beassociated with (different) four-step PUSCH/PUCCH resources.

In some cases, a preamble sequence may have a 1:1 correspondence with apayload resource, such that a single preamble sequence may be mapped tospecific payload resources. In some cases, however, it may be possibleto map multiple preamble sequences into the same payload (PUCCH/PUSCH)resource such that a preamble sequence shares a resource associationwith another preamble sequence. For example, preamble sequence 1 andsequence 2 may be mapped to the same PUSCH resource. In this case, abase station 205 may use additional information to distinguish betweenthe two preamble sequences. In some cases, different preamble sequencesmay be associated with different DMRS ports (e.g., different antennaports used to transmit the DMRS signal), or to different scramblingidentifiers (for both the DMRS and/or for transmission of the payloadportion). In this case, a base station 205 may use space divisionmultiple access (SDMA) techniques to separate sequence 1 and sequence 2.In some cases, a UE 210 may apply an additional differentiating factor,such as a different DMRS port or a different scrambling identifier, tothe uplink request message to allow differentiation of the payloadportion of the uplink request message. In some cases, a UE 210 may applyan additional identifying factor, such as a different DMRS port or adifferent scrambling identifier, to the uplink request message to allowidentification of the payload portion of the uplink request message.

In some cases, UEs 210 can further hash into (e.g., index) the multiplepayload resources/multiple DMRS ports/multiple scrambling IDs whenmultiple UEs 210 select the same preamble sequence. In some cases, thisapproach may help reduce collisions of transmissions from multiple UEs210 when the same preamble sequence is selected by multiple UEs 210.

FIG. 7 illustrates an example of a message configuration 700 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 700 may betransmitted using aspects of wireless communication system 100.

In some cases, message configurations 300, 400, 500, and 600 may beexamples of message configurations that may support a two-step RACHprocedure when the UE 210 may use a relatively small timing advance(TA), such as for communications within relatively small cells withcorrespondingly small TAs. A TA may be an offset (e.g., an amount oftime) that may be used to account for transmission time delays between aUE 210 and a base station 205 and thereby maintain synchronization ofdownlink and uplink transmissions. In some cases, if a cell issufficiently small (as may be, for example, in NR systems), the TA mayalso be small, and may be covered (e.g., spanned) by the CP of thepreamble portion of an uplink request message.

In some cases, however, the TA may be larger (or much larger) than theCP. Message configuration 700 may depict an example of a messageconfiguration that may support a two-step RACH procedure when the UE 210may use a relatively large TA. In this case, the UE 210 may transmit anuplink request message that includes a payload portion that istransmitted in a time-domain waveform and TDM-multiplexed with payloadsfor different UEs 210.

For example, message configuration 700 includes uplink request message705, which may be transmitted by a UE 210 to a base station 205 asdescribed with respect to FIG. 2. Uplink request message 705 may includea preamble portion 710 and a payload portion 725.

In some cases, the first preamble resource element 715-a in the preambleportion 710 includes a preamble cyclic prefix 720, and the subsequentpreamble resource elements 715 may be transmitted with or without theuse of preamble cyclic prefixes 720 between the preamble resourceelements 715. In some cases, cyclic prefix 720 may cover (e.g., span)the TA to allow preamble timing and channel estimation in the frequencydomain.

In some cases, payload portion 725 includes payload resource elements730-a through 740-c, each of which may or may not include acorresponding payload cyclic prefix 735; e.g., payload cyclic prefix 735may be optional. Payload portion 725 may include payload resourceelements for a first UE (e.g., payload resource elements 730-a through730-c) TDM multiplexed with payload resource elements for a second UE(e.g., payload resource elements 730-d through 730-e). In some cases,payload resource elements 730-d through 730-e for the second UE may notinclude payload cyclic prefixes. In some cases, payload resourceelements 730-a through 730-c and payload resource elements 730-d through730-e may include an embedded DMRS for their respective payload.

FIG. 8 illustrates an example of a message configuration 800 for anuplink request message of a two-step random access procedure inaccordance with aspects of the present disclosure. In some examples, anuplink request message having message configuration 800 may betransmitted using aspects of wireless communication system 100. Messageconfiguration 800 may depict an example of a message configuration thatmay support a two-step RACH procedure when the UE 210 may use arelatively large TA.

Message configuration 800 may be similar to message configuration 700,but in this example, the payload portion may include a time-domainwaveform with CDM-multiplexed payloads (rather than TDM-multiplexedpayloads) for different UEs 210.

For example, message configuration 800 includes uplink request message805, which may be transmitted by a UE 210 to a base station 205 asdescribed with respect to FIG. 2. Uplink request message 805 may includea preamble portion 810 and a payload portion 825.

In some cases, the first preamble resource element 815-a in the preambleportion 810 includes a preamble cyclic prefix 820, and the subsequentpreamble resource elements 815 may be transmitted with or without theuse of preamble cyclic prefixes 820 between the preamble resourceelements 815. In some cases, preamble cyclic prefix 820 may cover (e.g.,span) the TA to allow preamble timing and channel estimation in thefrequency domain.

In some cases, payload portion 825 includes payload resource elements830, each of which may or may not include a payload cyclic prefix 835.Payload portion 825 may include payload resource elements for a first UE(e.g., payload resource elements 830-a through 830-c) CDM multiplexedwith payload resource elements for a second UE (e.g., payload resourceelements 830-d through 830-f). In some cases, payload resource elements830-a through 830-c and payload resource elements 830-d through 830-fmay include a DMRS for the respective payload. In some cases, thepayload and the DMRS in the payload portion 825 may also be CDMmultiplexed using a different spreading code.

FIG. 9 shows a block diagram 900 of a device 905 that supports message 1of a two-step random access procedure in accordance with aspects of thepresent disclosure. The device 905 may be an example of aspects of a UE115 as described herein. The device 905 may include a receiver 910, a UEcommunications manager 915, and a transmitter 920. The device 905 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to message 1 ofa two-step random access procedure, etc.). Information may be passed onto other components of the device 905. The receiver 910 may be anexample of aspects of the transceiver 1220 described with reference toFIG. 12. The receiver 910 may utilize a single antenna or a set ofantennas.

The UE communications manager 915 may identify that the UE is configuredto use a two-step RACH procedure, the two-step RACH procedure includingan uplink request message and a downlink response. The UE communicationsmanager 915 may transmit the uplink request message as part of thetwo-step RACH procedure, the uplink request message including a preambleportion that is one of a set of predefined sequences and a payloadportion that includes a physical uplink shared channel waveform, wherethe preamble portion is associated with a transmission occasion of thePUSCH. The UE communications manager 915 may receive the downlinkresponse as part of the two-step RACH procedure and in response to theuplink request message. The UE communications manager 915 may be anexample of aspects of the UE communications manager 1210 describedherein.

The UE communications manager 915, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the UE communications manager 915, orits sub-components may be executed by a general-purpose processor, aDSP, an application-specific integrated circuit (ASIC), a FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The UE communications manager 915, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, the UEcommunications manager 915, or its sub-components, may be a separate anddistinct component in accordance with various aspects of the presentdisclosure. In some examples, the UE communications manager 915, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 920 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 920 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 920 may be an example of aspects of the transceiver 1220described with reference to FIG. 12. The transmitter 920 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a device 1005 that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure. The device 1005 may be an example ofaspects of a device 905, or a UE 115 as described herein. The device1005 may include a receiver 1010, a UE communications manager 1015, anda transmitter 1035. The device 1005 may also include a processor. Eachof these components may be in communication with one another (e.g., viaone or more buses).

The receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to message 1 ofa two-step random access procedure, etc.). Information may be passed onto other components of the device 1005. The receiver 1010 may be anexample of aspects of the transceiver 1220 described with reference toFIG. 12. The receiver 1010 may utilize a single antenna or a set ofantennas.

The UE communications manager 1015 may be an example of aspects of theUE communications manager 915 as described herein. The UE communicationsmanager 1015 may include an identifying manager 1020, a request messagemanager 1025, and a response manager 1030. The UE communications manager1015 may be an example of aspects of the UE communications manager 1210described herein.

The identifying manager 1020 may identify that the UE is configured touse a two-step RACH procedure, the two-step RACH procedure including anuplink request message and a downlink response.

The request message manager 1025 may transmit the uplink request messageas part of the two-step RACH procedure, the uplink request messageincluding a preamble portion that is one of a set of predefinedsequences and a payload portion that includes a waveform of a physicaluplink shared channel, where the preamble portion is associated with atransmission occasion of the physical uplink shared channel.

The response manager 1030 may receive the downlink response as part ofthe two-step RACH procedure and in response to the uplink requestmessage.

The transmitter 1035 may transmit signals generated by other componentsof the device 1005. In some examples, the transmitter 1035 may becollocated with a receiver 1010 in a transceiver module. For example,the transmitter 1035 may be an example of aspects of the transceiver1220 described with reference to FIG. 12. The transmitter 1035 mayutilize a single antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a UE communications manager 1105that supports message 1 of a two-step random access procedure inaccordance with aspects of the present disclosure. The UE communicationsmanager 1105 may be an example of aspects of a UE communications manager915, a UE communications manager 1015, or a UE communications manager1210 described herein. The UE communications manager 1105 may include anidentifying manager 1110, a request message manager 1115, a responsemanager 1120, a preamble manager 1125, a payload manager 1130, a cyclicprefix manager 1135, and an interleaving manager 1140. Each of thesemodules may communicate, directly or indirectly, with one another (e.g.,via one or more buses).

The identifying manager 1110 may identify that the UE is configured touse a two-step RACH procedure, the two-step RACH procedure including anuplink request message and a downlink response.

The request message manager 1115 may transmit the uplink request messageas part of the two-step RACH procedure, the uplink request messageincluding a preamble portion that is one of a set of predefinedsequences and a payload portion that includes waveform of a physicaluplink shared channel, where the preamble portion is associated with atransmission occasion of the physical uplink shared channel.

In some examples, the request message manager 1115 may transmit thepreamble portion of the uplink request message as a demodulationreference signal for the payload portion of the uplink request message.In some examples, the request message manager 1115 may transmitadditional demodulation reference signals for the payload portion of theuplink request message.

In some examples, the request message manager 1115 may receive, viaremaining minimum system information or radio resource controlsignaling, an association between the preamble portion of the uplinkrequest message and the payload portion of the uplink request message.

In some examples, the request message manager 1115 may transmit thepreamble portion of the uplink request message and the payload portionof the uplink request message without an intervening transmission timeinterval between the first transmission time interval and the secondtransmission time interval. In some examples, the request messagemanager 1115 may transmit the preamble portion of the uplink requestmessage and the payload portion of the uplink request message with anintervening transmission time interval between the first transmissiontime interval and the second transmission time interval, where theintervening transmission time interval is available for non-RACHtransmissions.

In some examples, the request message manager 1115 may apply anadditional differentiating factor to the uplink request message to allowdifferentiation of the payload portion of the uplink request message. Insome examples, the request message manager 1115 may apply an additionalidentifying factor to the uplink request message to allow identificationof the payload portion of the uplink request message. In some cases, theadditional differentiating factor is one or more of use of differentdemodulation reference signal ports or use of different scramblingidentifications. In some cases, the additional identifying factor is oneor more of use of different demodulation reference signal ports or useof different scrambling identifications.

The response manager 1120 may receive the downlink response as part ofthe two-step RACH procedure and in response to the uplink requestmessage.

The preamble manager 1125 may transmit the preamble portion of theuplink request message using a preamble sequence that has a prime numbersequence length.

In some examples, the preamble manager 1125 may transmit the preambleportion of the uplink request message back-to-back with the payloadportion of the uplink request message, each resource element of thepreamble portion and each resource element of the payload portion havinga cyclic prefix. In some examples, the preamble manager 1125 maytransmit the preamble portion of the uplink request message back-to-backwith the payload portion of the uplink request message without use ofcyclic prefixes between resource elements of the preamble portion. Insome examples, the preamble manager 1125 may transmit the preambleportion of the uplink request message during a first transmission timeinterval.

In some examples, the preamble manager 1125 may select a preamblesequence from the set of predefined sequences for transmission of thepreamble portion of the uplink request message, where only a portion ofthe predefined sequences are associated with two-step RACH procedures.In some examples, the preamble manager 1125 may select a preamblesequence from the set of predefined sequences for transmission of thepreamble portion of the uplink request message, where the selectedpreamble sequence shares a resource association with another preamblesequence of the set of predefined sequences. In some examples, thepreamble manager 1125 may select a preamble sequence from the set ofpredefined sequences for transmission of the preamble portion of theuplink request message, where the selected preamble sequence has aresource association with more than one payload resource.

In some examples, the preamble manager 1125 may receive an indication ofthe preamble portion.

The payload manager 1130 may transmit the payload portion using resourceelements that are a subset of a frequency span of the preamble portion.

In some examples, the payload manager 1130 may transmit the payloadportion using a payload size that is based, at least in part, on whetherthe two-step RACH procedure is for initial access or for handover. Insome examples, the payload manager 1130 may transmit the payload portionusing a fixed payload size. In some examples, the payload manager 1130may transmit, in accordance with the received association, the payloadportion of the uplink request message during a second transmission timeinterval.

In some examples, the payload manager 1130 may transmit the payloadportion of the uplink request message with an embedded demodulationreference signal to match dimensions of both the preamble portion andthe payload portion. In some examples, the payload manager 1130 maytransmit the payload portion during a time resource that istime-multiplexed with payload portions from additional UEs. In someexamples, the payload manager 1130 may transmit the payload portionduring a time resource that is code division-multiplexed with payloadportions from additional UEs.

The cyclic prefix manager 1135 may generate a cyclic prefix for resourceelements in the preamble portion and/or the payload portion.

In some cases, the cyclic prefix of the resource elements of thepreamble portion of the uplink request message is different from thecyclic prefix of the resource elements of the payload portion of theuplink request message.

The interleaving manager 1140 may transmit the preamble portion of theuplink request message interleaved in time with the payload portion ofthe uplink request message, each resource element of the preambleportion and each resource element of the payload portion having a cyclicprefix.

In some cases, the cyclic prefix of the resource elements of thepreamble portion of the uplink request message is different from thecyclic prefix of the resource elements of the payload portion of theuplink request message.

FIG. 12 shows a diagram of a system 1200 including a device 1205 thatsupports message 1 of a two-step random access procedure in accordancewith aspects of the present disclosure. The device 1205 may be anexample of or include the components of device 905, device 1005, or a UE115 as described herein. The device 1205 may include components forbi-directional voice and data communications including components fortransmitting and receiving communications, including a UE communicationsmanager 1210, an I/O controller 1215, a transceiver 1220, an antenna1225, memory 1230, and a processor 1240. These components may be inelectronic communication via one or more buses (e.g., bus 1245).

The UE communications manager 1210 may identify that the UE isconfigured to use a two-step RACH procedure, the two-step RACH procedureincluding an uplink request message and a downlink response, transmitthe uplink request message as part of the two-step RACH procedure, theuplink request message including a preamble portion that is one of a setof predefined sequences and a payload portion that includes a waveformof a physical uplink shared channel, where the preamble portion isassociated with a transmission occasion of the physical uplink sharedchannel, and receive the downlink response as part of the two-step RACHprocedure and in response to the uplink request message.

The I/O controller 1215 may manage input and output signals for thedevice 1205. The I/O controller 1215 may also manage peripherals notintegrated into the device 1205. In some cases, the I/O controller 1215may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 1215 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 1215may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 1215may be implemented as part of a processor. In some cases, a user mayinteract with the device 1205 via the I/O controller 1215 or viahardware components controlled by the I/O controller 1215.

The transceiver 1220 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1220 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1220 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1225.However, in some cases the device may have more than one antenna 1225,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1230 may include RAM and ROM. The memory 1230 may storecomputer-readable, computer-executable code 1235 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some cases, the memory 1230 may contain, amongother things, a BIOS which may control basic hardware or softwareoperation such as the interaction with peripheral components or devices.

The processor 1240 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1240 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 1240. The processor 1240 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 1230) to cause the device 1205 to perform variousfunctions (e.g., functions or tasks supporting message 1 of a two-steprandom access procedure).

The code 1235 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1235 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1235 may not be directly executable by theprocessor 1240 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 13 shows a block diagram 1300 of a device 1305 that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure. The device 1305 may be an example ofaspects of a base station 105 as described herein. The device 1305 mayinclude a receiver 1310, a base station communications manager 1315, anda transmitter 1320. The device 1305 may also include a processor. Eachof these components may be in communication with one another (e.g., viaone or more buses).

The receiver 1310 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to message 1 ofa two-step random access procedure, etc.). Information may be passed onto other components of the device 1305. The receiver 1310 may be anexample of aspects of the transceiver 1620 described with reference toFIG. 16. The receiver 1310 may utilize a single antenna or a set ofantennas.

The base station communications manager 1315 may receive, as part of atwo-step RACH procedure, an uplink request message from a UE, the uplinkrequest message including a preamble portion that is one of a set ofpredefined sequences and a payload portion that includes a waveform of aphysical uplink shared channel, where the preamble portion is associatedwith a transmission occasion of the physical uplink shared channel, andtransmit a downlink response as part of the two-step RACH procedure andin response to the uplink request message. The base stationcommunications manager 1315 may be an example of aspects of the basestation communications manager 1610 described herein.

The base station communications manager 1315, or its sub-components, maybe implemented in hardware, code (e.g., software or firmware) executedby a processor, or any combination thereof. If implemented in codeexecuted by a processor, the functions of the base stationcommunications manager 1315, or its sub-components may be executed by ageneral-purpose processor, a DSP, an application-specific integratedcircuit (ASIC), a FPGA or other programmable logic device, discrete gateor transistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described in the presentdisclosure.

The base station communications manager 1315, or its sub-components, maybe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, the basestation communications manager 1315, or its sub-components, may be aseparate and distinct component in accordance with various aspects ofthe present disclosure. In some examples, the base stationcommunications manager 1315, or its sub-components, may be combined withone or more other hardware components, including but not limited to aninput/output (I/O) component, a transceiver, a network server, anothercomputing device, one or more other components described in the presentdisclosure, or a combination thereof in accordance with various aspectsof the present disclosure.

The transmitter 1320 may transmit signals generated by other componentsof the device 1305. In some examples, the transmitter 1320 may becollocated with a receiver 1310 in a transceiver module. For example,the transmitter 1320 may be an example of aspects of the transceiver1620 described with reference to FIG. 16. The transmitter 1320 mayutilize a single antenna or a set of antennas.

FIG. 14 shows a block diagram 1400 of a device 1405 that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure. The device 1405 may be an example ofaspects of a device 1305, or a base station 105 as described herein. Thedevice 1405 may include a receiver 1410, a base station communicationsmanager 1415, and a transmitter 1430. The device 1405 may also include aprocessor. Each of these components may be in communication with oneanother (e.g., via one or more buses).

The receiver 1410 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to message 1 ofa two-step random access procedure, etc.). Information may be passed onto other components of the device 1405. The receiver 1410 may be anexample of aspects of the transceiver 1620 described with reference toFIG. 16. The receiver 1410 may utilize a single antenna or a set ofantennas.

The base station communications manager 1415 may be an example ofaspects of the base station communications manager 1315 as describedherein. The base station communications manager 1415 may include amessage receiving manager 1420 and a downlink response manager 1425. Thebase station communications manager 1415 may be an example of aspects ofthe base station communications manager 1610 described herein.

The message receiving manager 1420 may receive, as part of a two-stepRACH procedure, an uplink request message from a UE, the uplink requestmessage including a preamble portion that is one of a set of predefinedsequences and a payload portion that includes a waveform of a physicaluplink shared channel waveform, where the preamble portion is associatedwith a transmission occasion of the physical uplink shared channel.

The downlink response manager 1425 may transmit a downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.

The transmitter 1430 may transmit signals generated by other componentsof the device 1405. In some examples, the transmitter 1430 may becollocated with a receiver 1410 in a transceiver module. For example,the transmitter 1430 may be an example of aspects of the transceiver1620 described with reference to FIG. 16. The transmitter 1430 mayutilize a single antenna or a set of antennas.

FIG. 15 shows a block diagram 1500 of a base station communicationsmanager 1505 that supports message 1 of a two-step random accessprocedure in accordance with aspects of the present disclosure. The basestation communications manager 1505 may be an example of aspects of abase station communications manager 1315, a base station communicationsmanager 1415, or a base station communications manager 1610 describedherein. The base station communications manager 1505 may include amessage receiving manager 1510, a downlink response manager 1515, ademodulation manager 1520, a message transmitting manager 1525, apreamble receiving manager 1530, a payload receiving manager 1535, and ascheduling manager 1540. Each of these modules may communicate, directlyor indirectly, with one another (e.g., via one or more buses).

The message receiving manager 1510 may receive, as part of a two-stepRACH procedure, an uplink request message from a UE, the uplink requestmessage including a preamble portion that is one of a set of predefinedsequences and a payload portion that includes a waveform of a physicaluplink shared channel, where the preamble portion is associated with atransmission occasion of the physical uplink shared channel.

In some examples, the message receiving manager 1510 may receive thepreamble portion of the uplink request message. In some examples, themessage receiving manager 1510 may receive the preamble portion of theuplink request message using a preamble sequence that has a prime numbersequence length.

In some examples, the message receiving manager 1510 may receive thepayload portion using resource elements that are a subset of a frequencyspan of the preamble portion. In some examples, the message receivingmanager 1510 may receive the payload portion using a payload size thatis based, at least in part, on whether the two-step RACH procedure isfor initial access or for handover. In some examples, the messagereceiving manager 1510 may receive the payload portion using a fixedpayload size.

In some examples, the message receiving manager 1510 may receive thepreamble portion of the uplink request message back-to-back with thepayload portion of the uplink request message, each resource element ofthe preamble portion and each resource element of the payload portionhaving a cyclic prefix. In some examples, the message receiving manager1510 may receive the preamble portion of the uplink request messageinterleaved in time with the payload portion of the uplink requestmessage, each resource element of the preamble portion and each resourceelement of the payload portion having a cyclic prefix. In some examples,the message receiving manager 1510 may receive the preamble portion ofthe uplink request message back-to-back with the payload portion of theuplink request message without use of cyclic prefixes between resourceelements of the preamble portion.

In some examples, the message receiving manager 1510 may receive thepreamble portion of the uplink request message during a firsttransmission time interval. In some examples, the message receivingmanager 1510 may receive, in accordance with the association transmittedvia remaining minimum system information or radio resource controlsignaling, the payload portion of the uplink request message during asecond transmission time interval. In some examples, the messagereceiving manager 1510 may receive the preamble portion of the uplinkrequest message and the payload portion of the uplink request messagewithout an intervening transmission time interval between the firsttransmission time interval and the second transmission time interval. Insome examples, the message receiving manager 1510 may receive thepreamble portion of the uplink request message and the payload portionof the uplink request message with an intervening transmission timeinterval between the first transmission time interval and the secondtransmission time interval, where the intervening transmission timeinterval is available for non-RACH transmissions.

In some examples, the message receiving manager 1510 may receive in thepreamble portion a preamble sequence selected from the set of predefinedsequences, where only a portion of the predefined sequences areassociated with two-step RACH procedures. In some examples, the messagereceiving manager 1510 may receive the payload portion of the uplinkrequest message with an embedded demodulation reference signal to matchdimensions of both the preamble portion and the payload portion.

In some cases, the cyclic prefix of the resource elements of thepreamble portion of the uplink request message is different from thecyclic prefix of the resource elements of the payload portion of theuplink request message.

The downlink response manager 1515 may transmit a downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.

The demodulation manager 1520 may use the preamble portion of the uplinkrequest message as a demodulation reference signal for the payloadportion of the uplink request message.

In some examples, the demodulation manager 1520 may receive additionaldemodulation reference signals for the payload portion of the uplinkrequest message.

The message transmitting manager 1525 may transmit, via remainingminimum system information or radio resource control signaling, anassociation between the preamble portion of the uplink request messageand the payload portion of the uplink request message.

In some examples, the message transmitting manager 1525 may transmit anindication of the preamble portion.

The preamble receiving manager 1530 may receive in the preamble portiona preamble sequence selected from the set of predefined sequences, wherethe selected preamble sequence shares a resource association withanother preamble sequence of the set of predefined sequences.

In some examples, the preamble receiving manager 1530 may receive in thepreamble portion a preamble sequence selected from the set of predefinedsequences, where the selected preamble sequence has a resourceassociation with more than one payload resource.

The payload receiving manager 1535 may differentiate the payload portionof the uplink request message via a differentiating factor.

In some examples, the payload receiving manager 1535 may identify thepayload portion of the uplink request message via an identifying factor.In some examples, the payload receiving manager 1535 may receive thepayload portion during a time resource that is time-multiplexed withpayload portions from additional UEs. In some examples, the payloadreceiving manager 1535 may receive the payload portion during a timeresource that is code division-multiplexed with payload portions fromadditional UEs. In some cases, the identifying factor is one or more ofuse of different demodulation reference signal ports or use of differentscrambling identifications.

In some examples, the payload receiving manager 1535 may apply thepreamble portion of the uplink request message as a demodulationreference signal for the payload portion of the uplink request message.

In some cases, the differentiating factor is one or more of use ofdifferent demodulation reference signal ports or use of differentscrambling identifications.

The scheduling manager 1540 may schedule non-RACH transmissions based onpresence of the preamble portion and application of the preamble portionas a demodulation reference signal.

FIG. 16 shows a diagram of a system 1600 including a device 1605 thatsupports message 1 of a two-step random access procedure in accordancewith aspects of the present disclosure. The device 1605 may be anexample of or include the components of device 1305, device 1405, or abase station 105 as described herein. The device 1605 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including abase station communications manager 1610, a network base stationcommunications manager 1615, a transceiver 1620, an antenna 1625, memory1630, a processor 1640, and an inter-station base station communicationsmanager 1645. These components may be in electronic communication viaone or more buses (e.g., bus 1650).

The base station communications manager 1610 may receive, as part of atwo-step RACH procedure, an uplink request message from a UE, the uplinkrequest message including a preamble portion that is one of a set ofpredefined sequences and a payload portion that includes either aphysical uplink control channel waveform or a physical uplink sharedchannel waveform and transmit a downlink response as part of thetwo-step RACH procedure and in response to the uplink request message.

The network base station communications manager 1615 may managecommunications with the core network (e.g., via one or more wiredbackhaul links). For example, the network base station communicationsmanager 1615 may manage the transfer of data communications for clientdevices, such as one or more UEs 115.

The transceiver 1620 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1620 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1620 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1625.However, in some cases the device may have more than one antenna 1625,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1630 may include RAM, ROM, or a combination thereof. Thememory 1630 may store computer-readable code 1635 including instructionsthat, when executed by a processor (e.g., the processor 1640) cause thedevice to perform various functions described herein. In some cases, thememory 1630 may contain, among other things, a BIOS which may controlbasic hardware or software operation such as the interaction withperipheral components or devices.

The processor 1640 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1640 may be configured to operate a memoryarray using a memory controller. In some cases, a memory controller maybe integrated into processor 1640. The processor 1640 may be configuredto execute computer-readable instructions stored in a memory (e.g., thememory 1630) to cause the device 1605 to perform various functions(e.g., functions or tasks supporting message 1 of a two-step randomaccess procedure).

The inter-station base station communications manager 1645 may managecommunications with other base station 105, and may include a controlleror scheduler for controlling communications with UEs 115 in cooperationwith other base stations 105. For example, the inter-station basestation communications manager 1645 may coordinate scheduling fortransmissions to UEs 115 for various interference mitigation techniquessuch as beamforming or joint transmission. In some examples, theinter-station base station communications manager 1645 may provide an X2interface within an LTE/LTE-A wireless communication network technologyto provide communication between base stations 105.

The code 1635 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1635 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1635 may not be directly executable by theprocessor 1640 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 17 shows a flowchart illustrating a method 1700 that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure. The operations of method 1700 may beimplemented by a UE 115 or its components as described herein. Forexample, the operations of method 1700 may be performed by acommunications manager as described with reference to FIGS. 9 through12. In some examples, a UE may execute a set of instructions to controlthe functional elements of the UE to perform the functions describedbelow. Additionally or alternatively, a UE may perform aspects of thefunctions described below using special-purpose hardware.

At 1705, the UE may identify that the UE is configured to use a two-stepRACH procedure, the two-step RACH procedure including an uplink requestmessage and a downlink response. The operations of 1705 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1705 may be performed by an identifying manager asdescribed with reference to FIGS. 9 through 12.

At 1710, the UE may transmit the uplink request message as part of thetwo-step RACH procedure, the uplink request message including a preambleportion that is one of a set of predefined sequences and a payloadportion that includes a waveform of a physical uplink shared channel,where the preamble portion is associated with a transmission occasion ofthe physical uplink shared channel. The operations of 1710 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1710 may be performed by a request messagemanager as described with reference to FIGS. 9 through 12.

At 1715, the UE may receive the downlink response as part of thetwo-step RACH procedure and in response to the uplink request message.The operations of 1715 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1715may be performed by a response manager as described with reference toFIGS. 9 through 12.

FIG. 18 shows a flowchart illustrating a method 1800 that supportsmessage 1 of a two-step random access procedure in accordance withaspects of the present disclosure. The operations of method 1800 may beimplemented by a base station 105 or its components as described herein.For example, the operations of method 1800 may be performed by acommunications manager as described with reference to FIGS. 13 through16. In some examples, a base station may execute a set of instructionsto control the functional elements of the base station to perform thefunctions described below. Additionally or alternatively, a base stationmay perform aspects of the functions described below usingspecial-purpose hardware.

At 1805, the base station may receive, as part of a two-step RACHprocedure, an uplink request message from a UE, the uplink requestmessage including a preamble portion that is one of a set of predefinedsequences and a payload portion that a waveform of a physical uplinkshared channel, where the preamble portion is associated with atransmission occasion of the physical uplink shared channel. Theoperations of 1805 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1805 may beperformed by a message receiving manager as described with reference toFIGS. 13 through 16.

At 1810, the base station may transmit a downlink response as part ofthe two-step RACH procedure and in response to the uplink requestmessage. The operations of 1810 may be performed according to themethods described herein. In some examples, aspects of the operations of1810 may be performed by a downlink response manager as described withreference to FIGS. 13 through 16.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellmay be associated with a lower-powered base station 105, as comparedwith a macro cell, and a small cell may operate in the same or different(e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 115 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessby UEs 115 having an association with the femto cell (e.g., UEs 115 in aclosed subscriber group (CSG), UEs 115 for users in the home, and thelike). An eNB for a macro cell may be referred to as a macro eNB. An eNBfor a small cell may be referred to as a small cell eNB, a pico eNB, afemto eNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells, and may also support communicationsusing one or multiple component carriers.

The wireless communications system 100 or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations 105 may have similar frame timing, andtransmissions from different base stations 105 may be approximatelyaligned in time. For asynchronous operation, the base stations 105 mayhave different frame timing, and transmissions from different basestations 105 may not be aligned in time. The techniques described hereinmay be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA) or other programmable logic device (PLD), discretegate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read only memory (EEPROM), flash memory, compactdisk (CD) ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other non-transitory medium thatcan be used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. Disk and disc, as used herein, include CD, laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveare also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication at a userequipment (UE), comprising: identifying that the UE is configured to usea two-step random access channel (RACH) procedure, the two-step RACHprocedure including an uplink request message and a downlink response;transmitting the uplink request message as part of the two-step RACHprocedure, the uplink request message including a preamble portion thatis one of a plurality of predefined sequences and a payload portion thatcomprises a waveform of a physical uplink shared channel, wherein thepreamble portion is associated with a transmission occasion of thephysical uplink shared channel; and receiving the downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.
 2. The method of claim 1, further comprising: receivingan indication of the preamble portion before transmitting the uplinkrequest message.
 3. The method of claim 1, wherein transmitting theuplink request message comprises: transmitting the payload portion usinga payload size that is based, at least in part, on whether the two-stepRACH procedure is for initial access or for handover.
 4. The method ofclaim 1, wherein transmitting the uplink request message comprises:transmitting the payload portion using a fixed payload size.
 5. Themethod of claim 1, wherein transmitting the uplink request messagecomprises: transmitting the preamble portion of the uplink requestmessage back-to-back with the payload portion of the uplink requestmessage without use of cyclic prefixes between resource elements of thepreamble portion.
 6. The method of claim 1, further comprising:receiving, via remaining minimum system information or radio resourcecontrol signaling, an association between the preamble portion of theuplink request message and the payload portion of the uplink requestmessage.
 7. The method of claim 6, wherein transmitting the uplinkrequest message comprises: transmitting the preamble portion of theuplink request message during a first transmission time interval; andtransmitting, in accordance with the received association, the payloadportion of the uplink request message during a second transmission timeinterval.
 8. The method of claim 7, wherein transmitting the uplinkrequest message further comprises: transmitting the preamble portion ofthe uplink request message and the payload portion of the uplink requestmessage without an intervening transmission time interval between thefirst transmission time interval and the second transmission timeinterval.
 9. The method of claim 7, wherein transmitting the uplinkrequest message further comprises: transmitting the preamble portion ofthe uplink request message and the payload portion of the uplink requestmessage with an intervening transmission time interval between the firsttransmission time interval and the second transmission time interval,wherein the intervening transmission time interval is available fornon-RACH transmissions.
 10. The method of claim 1, further comprising:selecting a preamble sequence from the plurality of predefined sequencesfor transmission of the preamble portion of the uplink request message,wherein only a portion of the predefined sequences are associated withtwo-step RACH procedures.
 11. The method of claim 1, further comprising:selecting a preamble sequence from the plurality of predefined sequencesfor transmission of the preamble portion of the uplink request message,wherein the selected preamble sequence shares a resource associationwith another preamble sequence of the plurality of predefined sequences;and applying an additional differentiating factor to the uplink requestmessage to allow differentiation of the payload portion of the uplinkrequest message.
 12. The method of claim 11, wherein the additionaldifferentiating factor is one or more of use of different demodulationreference signal ports or use of different scrambling identifications.13. The method of claim 1, further comprising: selecting a preamblesequence from the plurality of predefined sequences for transmission ofthe preamble portion of the uplink request message, wherein the selectedpreamble sequence has a resource association with more than one payloadresource; and applying an additional identifying factor to the uplinkrequest message to allow identification of the payload portion of theuplink request message.
 14. The method of claim 13, wherein theadditional identifying factor is one or more of use of differentdemodulation reference signal ports or use of different scramblingidentifications.
 15. The method of claim 1, wherein transmitting theuplink request message comprises: transmitting the payload portionduring a time resource that is time-multiplexed with payload portionsfrom additional UEs.
 16. The method of claim 1, wherein transmitting theuplink request message comprises: transmitting the payload portionduring a time resource that is code division-multiplexed with payloadportions from additional UEs.
 17. A method for wireless communication ata base station, comprising: receiving, as part of a two-step randomaccess channel (RACH) procedure, an uplink request message from a userequipment (UE), the uplink request message including a preamble portionthat is one of a plurality of predefined sequences and a payload portionthat comprises a waveform of a physical uplink shared channel, whereinthe preamble portion is associated with a transmission occasion of thephysical uplink shared channel; and transmitting a downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.
 18. The method of claim 17, further comprising:transmitting an indication of the preamble portion to the UE beforereceiving the uplink request message.
 19. The method of claim 17,wherein receiving the uplink request message comprises: receiving thepayload portion using a payload size that is based, at least in part, onwhether the two-step RACH procedure is for initial access or forhandover.
 20. The method of claim 17, wherein receiving the uplinkrequest message comprises: receiving the payload portion using a fixedpayload size.
 21. The method of claim 17, wherein receiving the uplinkrequest message comprises: receiving the preamble portion of the uplinkrequest message back-to-back with the payload portion of the uplinkrequest message without use of cyclic prefixes between resource elementsof the preamble portion.
 22. The method of claim 17, further comprising:transmitting, via remaining minimum system information or radio resourcecontrol signaling, an association between the preamble portion of theuplink request message and the payload portion of the uplink requestmessage.
 23. The method of claim 22, wherein receiving the uplinkrequest message comprises: receiving the preamble portion of the uplinkrequest message during a first transmission time interval; andreceiving, in accordance with the transmitted association, the payloadportion of the uplink request message during a second transmission timeinterval.
 24. The method of claim 17, wherein receiving the uplinkrequest message further comprises: receiving in the preamble portion apreamble sequence selected from the plurality of predefined sequences,wherein only a portion of the predefined sequences are associated withtwo-step RACH procedures.
 25. The method of claim 17, wherein receivingthe uplink request message further comprises: receiving in the preambleportion a preamble sequence selected from the plurality of predefinedsequences, wherein the selected preamble sequence shares a resourceassociation with another preamble sequence of the plurality ofpredefined sequences; and differentiating the payload portion of theuplink request message via a differentiating factor.
 26. The method ofclaim 25, wherein the differentiating factor is one or more of use ofdifferent demodulation reference signal ports or use of differentscrambling identifications.
 27. The method of claim 17, whereinreceiving the uplink request message further comprises: receiving in thepreamble portion a preamble sequence selected from the plurality ofpredefined sequences, wherein the selected preamble sequence has aresource association with more than one payload resource; andidentifying the payload portion of the uplink request message via anidentifying factor.
 28. The method of claim 27, wherein the identifyingfactor is one or more of use of different demodulation reference signalports or use of different scrambling identifications.
 29. An apparatusfor wireless communication at a user equipment (UE), comprising: aprocessor, memory in electronic communication with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to: identify that the UE is configured to use atwo-step random access channel (RACH) procedure, the two-step RACHprocedure including an uplink request message and a downlink response;transmit the uplink request message as part of the two-step RACHprocedure, the uplink request message including a preamble portion thatis one of a plurality of predefined sequences and a payload portion thatcomprises a waveform of a physical uplink shared channel, wherein thepreamble portion is associated with a transmission occasion of thephysical uplink shared channel; and receive the downlink response aspart of the two-step RACH procedure and in response to the uplinkrequest message.
 30. An apparatus for wireless communication at a basestation, comprising: a processor, memory in electronic communicationwith the processor; and instructions stored in the memory and executableby the processor to cause the apparatus to: receive, as part of atwo-step random access channel (RACH) procedure, an uplink requestmessage from a user equipment (UE), the uplink request message includinga preamble portion that is one of a plurality of predefined sequencesand a payload portion that comprises a waveform of a physical uplinkshared channel, wherein the preamble portion is associated with atransmission occasion of the physical uplink shared channel; andtransmit a downlink response as part of the two-step RACH procedure andin response to the uplink request message.